Sure, farmers in Frankfurt might have been easier, that doesn't mean he's not right about every single of those lines.
Kovac knows he's losing his job in the upcoming weeks and he's telling his players what they have to hear as well. Those guys are not pulling their weight. Are they doing it on purpose? Possible. He has every right to make those fair criticisms however.
He's done a diabolical job so far in every aspect of management. That he's lashing out at his players with obvious observations (
Kimmich was playing too attacking? Really? You don't say! Boateng and Suele are not aggressive enough? Wow, such a novel statement!) as parting words this late in the game doesn't move the needle. He needed to instruct, improve, enhance, and instill confidence throughout the season. It's not like Kimmich or Boateng were playing particularly worse during this stretch - they haven't changed their games for the worse all season, it's been consistent from both of them.
The players are under-performing and lack confidence. They might have turned the corner, they might have not - we'll see this weekend. But 23 players have all declined in performance, that clearly indicates that there is a common denominator at play and not all 23 players are suddenly past it. We see individuals make individual mistakes. It isn't the team's core imploding, it is every player in every position who has been mis-firing and mis-playing - they're far too slow on the ball, they're not aggressive, they're not clever with their pressing, they're not challenging their opponents much at all. They coasted the early part of the season on talent and determination after a poor summer showing (Germans + Lewy and a few others) but since then they've been figured out tactically and Kovac has had no answers.
He should've hammered out their flaws earlier in the season, not at this stage. Better late than never though. That there is an obvious mole/leak (it seems to be Kimmich, no?) isn't good. For their sake, I hope it's sorted out sooner than later.